On the influence of storage time on the long-term breakdown characteristics of solid synthetic materials

The author presents results of accelerated voltage tests performed with two model arrangements reflecting conditions of degradation typical for cast epoxy and extruded low-density polyethylene insulations, i.e. internal PD (partial discharge) in regular voids and ET (electrical treeing) from sharp points. As the intervals from the time at which the specimens had been manufactured until the execution of the tests varied from 2 days up to 10 years, the results reflected the influence of storage time on the life of the specimens. No significant variations of inception voltage with storage time was observed for the void arrangement; however they are clearly visible for the point arrangement. Due to the low sensitivity of the method of measurement used in the latter case, differences relevant to sample preparation remained undetected.<
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